Document based character ambiguity resolution

ABSTRACT

Methods and apparatus for document based ambiguous character resolution. An application searches a document for words that do not contain ambiguous characters and adds them to a dictionary, then searches the document for words that do contain ambiguous characters. For each ambiguous word, a set of candidate solutions is created by resolving the ambiguous characters in all possible ways. The dictionary is searched for words matching members of the candidate solution set. When a single member is matched, the ambiguous characters are resolved accordingly. When no member or more than one member is matched, a user is prompted to resolve the ambiguous characters. Alternatively, when more than one member is matched, the ambiguous characters are resolved to obtain the largest word, the smallest word, the most words, or the fewest words.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, and claims the benefit of priority to, U.S. application Ser. No. 09/774,191, filed on Jan. 29, 2001, the disclosure of which is herein incorporated by reference.

BACKGROUND

The invention relates to the field of resolving character ambiguities.

In modern offices, documents are routinely scanned into computers where they are stored as electronic images. While these images allow users to view the contents of the scanned documents, they do not allow users to manipulate the contents using standard word processing utilities. For example, users cannot find and replace a word in a scanned document stored as an electronic image. Optical character recognition algorithms attempt to recognize text occurring in scanned document images, and store the text in a formatted file that is comprehensible to a word processing algorithm. Examples of formatted files include Unicode files, and ASCII files. However, since optical character recognition algorithms are not 100% efficient, they occasionally misidentify words and characters in a scanned document, or encounter ambiguous words and characters which they cannot resolve.

One ambiguity encountered by optical character recognition algorithms is whether a hyphen occurring in a hyphenated word is a hard hyphen or soft hyphen. Hard hyphens are hyphens which belong in a word, such as the hyphens in the word daughter-in-law. Soft hyphens are hyphens which are inserted into a word by a word-processor or word-processing application for typesetting purposes only. Soft hyphens typically occur at the end of a line of text and are inserted to divide a word into two word fragments, the first of which remains on the current line of text followed by the soft hyphen, while the second begins a new line of text. Soft hyphens and hard hyphens are represented differently in formatted files. For example, soft hyphens are represented in Unicode formatted files by the hexadecimal word 00AD, while hard hyphens are represented by the hexadecimal word 002D. When an optical character recognition algorithm encounters a hyphen in a hyphenated word, it needs to identify the hyphen as either a hard hyphen or a soft hyphen so that it can store the hyphen with the appropriate code in the formatted output file. That way, a subsequent word processing application reading the formatted file can correctly interpret the hyphen to correctly display the word in which the hyphen appears.

Another ambiguity encountered by optical character recognition algorithms is whether white space between two characters in a string of characters is mere kerning between the characters in a word or a word separator. All characters in a typeset document are separated by white space. Within a word, the white space between characters is called kerning and is put there to give the characters and the word a visually pleasing appearance. Typically, the kerning between characters in a word is less than 1/20 of an em in length. (An em is a unit of typeset distance, and is roughly equal to the width of the letter ‘M’ in a given font and point size.) Between words, the white space in a document is called a blank space, or simply a space. Typically, blank spaces are ½ an em in length, or larger. When an optical character recognition algorithm encounters a string of characters where two or more characters in the string are separated by one or more white spaces too big to be unambiguously kerning (greater than 1/20 of an em), yet too small to be unambiguously blank spaces (smaller than ½ an em), the algorithm must correctly resolve each white space into kerning or blank space to correctly group the character string into one or more words, as appropriate.

SUMMARY

A method for identifying and correcting ambiguous amounts of white spaces in an electronic document is disclosed. An electronic document is searched for a character sequence that is separated on its ends by blank spaces, and that contains one or more adjacent pairs of characters that are separated by an ambiguous amount of white space that is too large to be kerning space but too small to be a blank space. When such a character sequence is found, a solution set is created for the character sequence by identifying the ambiguous white space between each pair of characters in the character sequence that is separated by an ambiguous white space as either a blank space or a kerning space. Each solution in the solution set corresponds to a unique identification of the ambiguous white spaces in the character sequence, and the entire set of solutions corresponds to all possible ways of identifying the ambiguous white spaces in the character sequence. Depending on the number of ambiguous white spaces, and how they are identified, each solution in the solution set can consist of a single character sequence or multiple character sequences. Some or all of the character sequences that are created in any solution in the solution set may or may not be found in an electronic dictionary.

An electronic dictionary is then searched to determine whether any of the solutions in the solution set match the dictionary. For a solution in the solution set to match the dictionary, each character sequence in the solution must be found in the dictionary. Thus, when a solution contains multiple character sequences, each character sequence in the solution must be found in the dictionary. The dictionary search results are then used to identify all of the ambiguous white spaces in the character sequence as either blank spaces or kerning spaces.

Advantages of the method include one or more of the following. When the dictionary only matches a single solution in the solution set, the ambiguous white spaces in the character sequence are identified in conformity with the identifications that were used to generate that solution. When the dictionary matches none of the solutions in the solution set, a user is prompted to manually identify each of the ambiguous white spaces in the character sequence as either a blank space or a kerning space. In one implementation, the user is prompted by being presenting with each solution in the solution set. When the user responds to the prompt, e.g., by accepting a particular solution, the ambiguous white spaces in the character sequence are identified in conformity with the identification that was used to create the accepted solution.

When the dictionary search matches more than one solution in the solution set, the method checks whether the user prefers the solution containing the largest word, the smallest word, the most words, or the fewest words. In one implementation, the user's preference is determined from a preference file. In another implementation, the user's preference is determined by prompting the user to indicate whether the user wishes to selected the solution containing the largest word, the smallest word, the most words, or the fewest words. If the user prefers not to select the solution containing the largest word, the smallest word, the most words, or the fewest words, the method prompts the user to manually identify each of the ambiguous white spaces in the character sequence as described above. Conversely, if the user prefers to select the solution containing the largest word, the smallest word, the most words, or the fewest words, the method identifies each of the ambiguous white spaces in the character sequence in conformity with identification used to create the solution having the largest word, the smallest word, the most words, or the fewest words.

The method can also be used to identify character sequences that are separated on their ends by blank spaces, and that do not contain any adjacent pairs of characters that are separated by an amount of white space that is larger than a kerning space. Such character sequences are recognized as words, and automatically added to the dictionary. In one implementation the dictionary is initially empty and is filled with words that are recognized in the received document. In another implementation, the dictionary is not empty, and can be a commercial electronic dictionary or a dictionary obtained by processing a previously received document, and new words are added to the dictionary as described.

The method allows character sequences found in a received electronic document that contain ambiguous white spaces to be resolved without having to access a commercial electronic reference dictionary, by creating and filling a dictionary with character sequences that do not contain ambiguous white spaces from the document being processed. The method thus uses the document itself as its own dictionary. In doing so, the method allows character sequences found in technical, medical, or foreign language documents that contain ambiguous white spaces to be resolved without having to access specialized technical, medical, or foreign language dictionaries.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a flow chart depicting a method for creating an electronic dictionary from an electronic document.

FIG. 2 is a flow chart depicting a method for resolving ambiguous characters in an electronic document using the document as its own dictionary.

FIG. 3A is a schematic illustration showing the construction of a set of candidate solutions for an ambiguous word.

FIG. 3B is a schematic illustration showing the construction of an alternative set of candidate solutions for the ambiguous word of FIG. 3A.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

An application capable of creating an electronic dictionary from an electronic document, and of using that dictionary to resolve ambiguous words in the electronic document is depicted in FIG. 1. The application receives an electronic document (step 101), and then creates and initializes a dictionary (step 102). Next, the application loops through the received document (steps 103-105), and searches for unambiguous words in the document (step 103) which it automatically adds to its dictionary (step 104), until all of the words in the document have been considered (step 105). The application considers a word unambiguous if the word does not contain any ambiguous characters or typesetting placeholders. Typesetting placeholders are symbols, characters, or commands which are put in a document to format the document or parts of the document, but which are not substantive parts of the document. Examples of typesetting placeholders include, but are not limited to, spaces, hyphens, commas, tabs, and end-of-line characters.

The application allows ambiguous words in a received document to be resolved without accessing a commercial electronic reference dictionary by filling its internally created dictionary with unambiguous words from the document being processed. In doing so, the application allows ambiguous typesetting placeholders in technical, medical, or foreign language words to be resolved without having access to specialized technical, medical, or foreign language dictionaries.

Once the application has searched the received document and automatically added all non-ambiguous words to its dictionary (steps 103-105), it checks whether it has access to a pre-existing dictionary (step 106). If it does, the application adds the contents of the pre-existing dictionary to its internally created dictionary (step 107). The pre-existing dictionary may be a pre-existing commercial electronic dictionary, or it may be a pre-existing electronic dictionary created by the application from one or more previously processed electronic documents.

With the full electronic dictionary, the application loops through the received document a second time (steps 108-110), and searches for ambiguous words (step 108) which it resolves and corrects using its dictionary (step 109). The second loop through the document terminates when all of the words in the document have been considered (step 110). The application considers a word ambiguous (step 108) if the word contains one or more ambiguous typesetting placeholders. For example, the application considers a word containing a hyphen at the end of a line ambiguous since the hyphen can be either a hard hyphen belonging to and separating the parts of a compound word, or a soft hyphen dividing the word across two lines by its syllables. Once the application has found (step 108), resolved and corrected (step 109) all of the ambiguous words in the received document, it saves the corrected electronic document and its internally created dictionary (step 110), and ends processing (step 111).

When the application finds an ambiguous word (step 108), it uses its dictionary to resolve and correct the word's ambiguities according to the method depicted in FIG. 2. For each word containing one or more ambiguous characters or typesetting placeholders (step 201), the application creates a complete set of candidate solutions (step 202). A candidate solution for an ambiguous word is created by resolving the one or more ambiguous characters or typesetting placeholders occurring in the word. Depending on the number and type of ambiguous typesetting placeholders in the word, and the method of resolving them, the candidate solution can consist of a single character string or of multiple character strings. Some or all of the character strings in a candidate solution may or may not be words in the application's dictionary. A complete set of candidate solutions for an ambiguous word is created by resolving the one or more ambiguous typesetting placeholders occurring in the ambiguous word in all possible ways.

For example, consider the word daughter-in-law as it is written in a small text box 300 in FIG. 3A, where a word processing algorithm has ambiguously hyphenated the word to fit within text box 300. A candidate solution is created for the word by separately resolving each of the three hyphens occurring in the word. Since each hyphen in daugh-ter-in-law is binary-resolvable, i.e., since each hyphen can be resolved in one of two ways as either a hard hyphen or as a soft hyphen, the set of three hyphens in the word can be resolved in eight different ways, yielding a set of candidate solutions containing eight members.

For example, one candidate solution is created by resolving all three hyphens as soft hyphens. That solution consists of the single character string daughterinlaw, shown as candidate solution 301 in FIG. 3A. Another candidate solution is created by resolving all three hyphens as hard hyphens. That solution consists of the four character strings daugh, ter, in, and law shown as candidate solution 308 in FIG. 3A. If all three hyphens in daugh-ter-in-law really are hard hyphens, each of the four character strings in candidate solution 308 ought to be found as a word in the application's dictionary since by definition hard hyphens separate compound words. The complete set of candidate solutions for the ambiguously hyphenated word daugh-ter-in-law is shown in FIG. 3A, and consists of the eight candidate solutions 301-308.

An alternative set of candidate solutions for the ambiguously hyphenated word daugh-ter-in-law is shown in FIG. 3B as candidate solutions 311-318. In FIG. 3B, each candidate solution is obtained by uniquely resolving each of the three hyphens in daugh-ter-in-law, as before. However, whereas the candidate solutions in FIG. 3A were created by separating candidate character strings containing hard hyphens into their component strings, all candidate solutions in FIG. 3B are created as single character strings, some of which contain hard hyphens. Thus, for example, where the three hyphens in daugh-ter-in-law are resolved as soft, hard, and soft hyphens, respectively, candidate solution 303 in FIG. 3A contains the two candidate character strings daughter and inlaw, whereas corresponding alternative candidate solution 313 in FIG. 3B contains the single candidate character string daughter-inlaw.

Once the application has created the set of candidate solutions for an ambiguous word (step 202), it loops through the candidate solution set, and searches its dictionary for matches to each candidate solution set member (step 203). For a candidate solution set member to match the dictionary search, each character string in the candidate solution set member must be found in the dictionary. Thus, in FIG. 3A, candidate solution set member 301 will not match a dictionary search since the character string daughterinlaw will not be found in any dictionary. Similarly, candidate solution set member 302 will not match a dictionary search since the character string daughterin will not be found in any dictionary, although the character string law will be. The only candidate solution set member in FIG. 3A which will match a dictionary search is solution 304 since each of the candidate character strings daughter, in, and law, will be found in the dictionary.

If only a single candidate solution set member matches the dictionary search, the search is deemed conclusive. The application checks whether a candidate solution set search is conclusive (step 204). If it is, the application resolves the ambiguous typesetting placeholders occurring in the ambiguous word according to the unique resolution used to create the single matching candidate solution set member (step 205), then exits (step 212). For example, assuming the words daughter, in, and law were used elsewhere in the received document, candidate solution set member 304 in FIG. 3A would be a conclusive solution to the ambiguously hyphenated word daugh-ter-in-law, since it is the only solution set member that would match the dictionary search as described above. Thus, the application would resolve daugh-ter-in-law by resolving the three hyphens in the word to conform to the unique resolutions used to create candidate solution set member 304. That is, it would respectively resolve the hyphens as soft, hard, and hard hyphens to obtain the word daughter-in-law.

If the dictionary search is inconclusive (step 204), it could be inconclusive because no candidate solution set member matched the dictionary search, or because more than one candidate solution set member matched the dictionary search. If no candidate solution set member matched the dictionary search (step 206), the application prompts a user to manually resolve the ambiguous word (step 208). In one implementation, the application prompts the user by presenting the user with all possible ambiguity resolutions, i.e., by presenting the user with each of the solutions in the set of candidate solutions. When the user responds to the prompt, e.g., by accepting a candidate solution set member, the application receives the user resolution and updates both the received document and the application's dictionary with the resolved word or words (step 209), before exiting (step 212).

If the dictionary search result is inconclusive because more than one candidate solution set member matched the search (step 206), the application checks whether the user prefers the candidate solution set member containing the largest word (step 210). The user's preference can be pre-determined from a preference file, or can be determined by prompting the user at step 210 to indicate whether the user wishes to select the candidate solution set member containing the largest matching word. If the user prefers not to select the candidate solution set member containing the largest matching word (step 210), the application prompts the user to resolve the ambiguous word (step 208), as described above. If the user prefers to select the candidate solution set member containing the largest matching word (step 210), the application resolves the ambiguous typesetting placeholders in conformity with the resolution used to create the candidate solution set member having the largest matching word (step 211). The application then updates the received document with the resolved word or words, and adds them to its dictionary (step 209), before exiting (step 212).

The invention can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. Apparatus of the invention can be implemented in a computer program product tangibly embodied in a machine-readable storage device for execution by a programmable processor; and method steps of the invention can be performed by a programmable processor executing a program of instructions to perform functions of the invention by operating on input data and generating output. The invention can be implemented advantageously in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. Each computer program can be implemented in a high-level procedural or object-oriented programming language, or in assembly or machine language if desired; and in any case, the language can be a compiled or interpreted language. Suitable processors include, by way of example, both general and special purpose microprocessors. Generally, a processor will receive instructions and data from a read-only memory and/or a random access memory. Generally, a computer will include one or more mass storage devices for storing data files; such devices include magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and optical disks. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM disks. Any of the foregoing can be supplemented by, or incorporated in, ASICs (application-specific integrated circuits).

To provide for interaction with a user, the invention can be implemented on a computer system having a display device such as a monitor or LCD screen for displaying information to the user and a keyboard and a pointing device such as a mouse or a trackball by which the user can provide input to the computer system. The computer system can be programmed to provide a graphical user interface through which computer programs interact with users.

A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, while the invention has been described in terms of resolving the ambiguously hyphenated word daugh-ter-in-law, it can obviously be used to resolve other ambiguously hyphenated words containing one or more ambiguous hyphens.

The invention can be used to resolve words that are ambiguous because they contain other ambiguous typesetting placeholders like ambiguous amounts of white space between characters, or ambiguous tabs or end-of-line characters. For example, the invention can be used to resolve the ambiguously separated word, car pool, into either the two words car and pool separated by an appropriate amount of blank space, or the single word carpool separated by an appropriate amount of kerning. The invention can be used to separate words containing one or more combinations of ambiguous typesetting placeholders, such as a word containing both ambiguous hyphens and ambiguous white space between characters.

Some or all of the steps described in the invention may be eliminated, or may be performed in a different order than has been described. For example, step 107 could be eliminated and the invention could be used without adding the contents of a pre-existing dictionary to the dictionary created by the application from the document being processed. Or the order of steps 102-105 and steps 106-107 could be reversed, so that the application starts with a pre-existing dictionary and automatically adds unambiguous words to the dictionary from the document being processed.

While the invention has been described as resolving an ambiguous word resulting in a dictionary search matching more than one candidate solution set members by selecting the candidate solution set member containing the largest word, it can also be implemented to resolving the ambiguous word by selecting the candidate solution set member containing the smallest word, the most words, or the fewest words.

While the method has been described as a step to resolve character ambiguities encountered in an optical character recognition process run on scanned documents, the method can also be used on its own or in conjunction with other applications to resolve character ambiguities. For example, the method can be used to resolve character ambiguities in an electronic document created by sending the output of a word processing program through a printer driver and directly to an alternatively formatted electronic document. For example, the method can be used to resolve character ambiguities created by sending the output of a word processing program through the PDFWriter® printer driver available from Adobe Systems Incorporated of San Jose, Calif., to a document formatted in the Portable Document Format. These and other implementations are within the scope of the following claims. 

1. A computer program product, stored on a machine-readable medium, comprising instructions operable to cause a programmable processor to: search a document for a character sequence that is separated on its ends by blank spaces, such that one or more adjacent pairs of characters in the character sequence are separated by an amount of white space that is ambiguous because it is larger than a kerning space but smaller than a blank space; create a solution set for the character sequence, wherein each solution in the solution set is obtained by identifying the ambiguous amount of white space between each pair of characters in the character sequence that is separated by an ambiguous amount of white space as either a blank space or a kerning space; search a dictionary for each solution in the solution set; and use the results from the dictionary search to identify the ambiguous amount of white space between each pair of characters in the character sequence that is separated by an ambiguous amount of white space as either a blank space or a kerning space.
 2. The computer program product of claim 1, wherein the result of the dictionary search is to find only one solution in the solution set, further comprising instructions operable to cause a programmable processor to identify the ambiguous amount of white space between each pair of characters in the character sequence that is separated by an ambiguous amount of white space in conformity with the one solution found in the dictionary search.
 3. The computer program product of claim 1, wherein the result of the dictionary search is to find none of the solutions in the solution set, further comprising instructions operable to cause a programmable processor to prompt a user to manually identify the ambiguous amount of white space between each pair of characters in the character sequence that is separated by an ambiguous amount of white space as either a blank space or a kerning space.
 4. The computer program product of claim 1, wherein the result of the dictionary search is to find more than one solution in the solution set, further comprising instructions operable to cause a programmable processor to prompt a user to manually resolve the ambiguous amount of white space between each pair of characters in the character sequence that is separated by an ambiguous amount of white space as either a blank space or a kerning space.
 5. The computer program product of claim 1, wherein the result of the dictionary search is to find more than one solution in the solution set, further comprising instructions operable to cause a programmable processor to identify the ambiguous amount of white space between each pair of characters in the character sequence that is separated by an ambiguous amount of white space in conformity with that solution containing the longest word.
 6. The computer program product of claim 1, wherein the result of the dictionary search is to find more than one solution in the solution set, further comprising instructions operable to cause a programmable processor to identify the ambiguous amount of white space between each pair of characters in the character sequence that is separated by an ambiguous amount of white space in conformity with that solution containing the most words.
 7. The computer program product of claim 1, wherein the result of the dictionary search is to find more than one solution in the solution set, further comprising instructions operable to cause a programmable processor to identify the ambiguous amount of white space between each pair of characters in the character sequence that is separated by an ambiguous amount of white space in conformity with that solution containing the shortest word.
 8. The computer program product of claim 1, wherein the result of the dictionary search is to find more than one solution in the solution set, further comprising instructions operable to cause a programmable processor to identify the ambiguous amount of white space between each pair of characters in the character sequence that is separated by an ambiguous amount of white space in conformity with that solution containing the fewest words.
 9. The computer program product of claim 1, further comprising instructions operable to cause a programmable processor to: identify a character sequence that is separated on its ends by blank spaces, such that no adjacent pairs of characters in the character sequence are separated by an amount of white space that is larger than a kerning space; and automatically add the character sequence to the dictionary.
 10. A method for identifying and correcting ambiguous amounts of white spaces in an electronic document, the method comprising: searching the document for a character sequence that is separated on its ends by blank spaces, such that one or more adjacent pairs of characters in the character sequence are separated by an amount of white space that is ambiguous because it is larger than a kerning space but smaller than a blank space; creating a solution set for the character sequence, wherein each solution in the solution set is obtained by identifying the ambiguous amount of white space between each pair of characters that is separated by an ambiguous amount of white space as either a blank space or a kerning space; searching a dictionary for each solution in the solution set; and using the results from the dictionary search to identify the ambiguous amount of white space between each pair of characters in the character sequence that is separated by an ambiguous amount of white space as either a blank space or a kerning space.
 11. The method of claim 1, wherein the result of the dictionary search is to find only one solution in the solution set, further comprising identifying the ambiguous amount of white space between each pair of characters in the character sequence that is separated by an ambiguous amount of white space in conformity with the one solution found in the dictionary search.
 12. The method of claim 1, wherein the result of the dictionary search is to find none of the solutions in the solution set, further comprising prompting a user to manually identify the ambiguous amount of white space between each pair of characters in the character sequence that is separated by an ambiguous amount of white space as either a blank space or a kerning space.
 13. The method claim 1, wherein the result of the dictionary search is to find more than one solution in the solution set, further comprising prompting a user to manually resolve the ambiguous amount of white space between each pair of characters in the character sequence that is separated by an ambiguous amount of white space as either a blank space or a kerning space.
 14. The method claim 1, wherein the result of the dictionary search is to find more than one solution in the solution set, further comprising identifying the ambiguous amount of white space between each pair of characters in the character sequence that is separated by an ambiguous amount of white space in conformity with that solution containing the longest word.
 15. The method claim 1, wherein the result of the dictionary search is to find more than one solution in the solution set, further comprising identifying the ambiguous amount of white space between each pair of characters in the character sequence that is separated by an ambiguous amount of white space in conformity with that solution containing the most words.
 16. The method claim 1, wherein the result of the dictionary search is to find more than one solution in the solution set, further comprising identifying the ambiguous amount of white space between each pair of characters in the character sequence that is separated by an ambiguous amount of white space in conformity with that solution containing the shortest word.
 17. The method of claim 1, wherein the result of the dictionary search is to find more than one solution in the solution set, further comprising identifying the ambiguous amount of white space between each pair of characters in the character sequence that is separated by an ambiguous amount of white space in conformity with that solution containing the fewest words.
 18. The method of claim 1, further comprising: identifying a character sequence that is separated on its ends by blank spaces, such that no adjacent pairs of characters in the character sequence are separated by an amount of white space that is larger than a kerning space; and automatically adding the character sequence to the dictionary. 